Rafael Nadal has pulled out of his proposed exhibition with world No. 1 Novak Djokovic at Real Madrid's Santiago Bernabeu Stadium on account of injury.

Nadal is back in his native Spain after his shock exit to Lukas Rosol in the second round of Wimbledon. During that defeat, Nadal slipped on a couple of occasions and he has picked up a knee injury that requires a fortnight's rest.

With his 'Alma Nadal' exhibition with Djokovic due to take place on July 14, Nadal has been forced to pull out of the charity contest.

"I want to apologise to everyone, especially to the fans who had bought lots of tickets for such a great cause," Nadal told Real's official website.

Nadal travelled to Vitoria for a specialist assessment on his knee and he has been advised to rest in order to ease the patella problem.

"I have also apologised to Novak Djokovic who selflessly gave up his time to play in this event," Nadal said, adding that he hoped to find a date later in the year to stage the event which is in aid of his foundation.